Heretofore, a display device is devised which can switch two-dimensional display and three-dimensional display over to each other such that, for example, characters or the like are plane-displayed with high resolution being maintained and illustrations or the like are stereo-displayed. With regard to the stereo display method, there are proposed many systems such as a twin-lens system utilizing a binocular parallax, and a holography system for drawing a three-dimensional image in a space. However, these systems have both merits and demerits.
For example, the twin-lens system stereo display method which is in the progress of generally coining into wide use is a display system which can simply realize a binocular vision. In the case of this twin-lens system stereo display method, appearance of solidity is obtained by using only the binocular parallax as a physiological factor for the binocular vision. Actually, however, with regard to the physiological factor for the binocular vision, there are many factors such as the binocular parallax, vergence, focus adjustment, and a kinematic parallax. Thus, in the case of the twin-lens system stereo display method, it is pointed out that a contradiction is caused against other factors, and due to this contradiction thus caused, a viewer is easy to fatigue as compared with the case of a two-dimensionally displayed image.
In addition, for example, in the case of the holography system, a wavefront of a light can be reconstructed. As a result, all the physiological factors for the binocular vision can be fulfilled, and thus it is possible to obtain the natural stereo display which gives the viewer the less feeling of fatigue. Actually, in a hologram (still image) which is made on a dry plate by using a laser interference, such a stereo image as to have a strong resemblance to the real thing is obtained. However, in the case of electronic display, an amount of necessary data is enormous, and also a device is absent which can be controlled on the micron order or less as in the dry plate. Therefore, under the circumstances, it is very difficult to display a color stereo moving image.
Moreover, with regard to another method, for example, there is known a method called an integral photography method (hereinafter referred to as “an IP method”) using many parallax images. This system is a relatively simple system composed of a lens array and a light source. Also, this system is a more real display system in which it is unnecessary for an observer to wear glasses, and an angle at which a stereo image is viewed changes depending on observing angles. For this reason, this system is expected as a stereo display system of the next generation.
That is to say, with this system, for a dedicated image which is two-dimensionally displayed, lights from pixels are deflected by the lens array, thereby generating parallaxes. Some lens arrays use solid micro-lenses, while a liquid lens with which a light is refracted by utilizing an interface between layers of liquids, thereby allowing a focal length to be freely changed can also be used in this lens array (for example, refer to Japanese Patent Laid-Open No. 2000-347005, U.S. Pat. No. 5,659,330, and Japanese Patent Laid-Open No. 2002-357774). By using such a liquid lens, a method of displaying an image, for example, switching between two-dimensional display and three-dimensional display can be readily carried out.
However, in the case of this system, when a lens system is made small in order to increase the resolution of the stereo display in a certain arbitrary pixel, the number of parallaxes (the number of pixels) in a unit lens decreases accordingly. Conversely, when a lens diameter is increased in order to increase the number of parallaxes, the resolution for the stereo display is reduced. That is to say, the increase in resolution for the stereo display and the increase in number of parallaxes as a barometer of the degree of solid show a relationship of tradeoff.
With regard to a method of increasing the number of parallaxes, for example, there is known a method of relatively moving a micro-lens array with respect to a luminescent pixel, thereby refracting the light in a plurality of directions (for example, refer to Japanese Patent Laid-Open No. 2002-176660). In addition, there is also known a method of controlling a position of a liquid droplet of the liquid lens (for example, refer to Japanese Patent Laid-Open No. 2003-215478).
However, for example, in the case of the method described in Japanese Patent Laid-Open No. 2003-215478, no concrete method with respect to the control for the position of the droplet is described. Even when the position of the liquid droplet is simply changed, for example, the lights emitted from the adjacent pixels overlap each other, a position where no light is emitted occurs, and so forth due to such a simple change unless the directions of emission of the lights (a refractive index or the like) can be properly controlled. Thus, there is the possibility that no image is properly displayed. That is to say, there is the possibility that the image quality of the output image is reduced.